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Optoelectronics/Displays??

Integrated LED driver features dimming control

Posted: 01 Oct 2007 ?? ?Print Version ?Bookmark and Share

Keywords:switch-mode LED driver? PWM dimming control? high-brightness?

A highly integrated LED driver with analog and PWM dimming control has been introduced by Maxim Integrated Products. The MAX16812 high-voltage, high-brightness (HB), switch-mode LED driver integrates a high-side/differential LED current-sense amplifier, a PWM-dimming MOSFET driver, and a 76V-rated, 0.2? switching MOSFET.

The use of an internal dimming MOSFET driver enhances system reliability by automatically switching off power to the LED strings during automotive load-dump events. To ensure even brightness matching, the MAX16812 provides 5 percent accurate LED-current control. An on-board, 200Hz ramp generator allows PWM-dimming control with an external analog signal, or it can be synchronized to an external PWM signal. Linearly controlled PWM dimming greatly simplifies implementation of two-level brightness control and theater dimming. During PWM dimming, the MAX16812 controls the LED current rise and fall times to suppress EMI and system noise. An external resistor can be connected between the gate driver and internal switching MOSFET for control of the switching current rise and fall times.

The MAX16812 provides 100-500kHz operating-frequency range for maximum flexibility, and operates from a 5.5-76V supply-voltage range, ensuring cold-start and load-dump compliance. It is fully specified over the -40 degrees Celsius to +125Celsius automotive temperature range, and is available in a thermally enhanced, 5mm x 5mm, 28-pin TQFN package.

Designed to withstand harsh operating environments, this HB LED driver also features overvoltage protection, undervoltage lockout, soft-start, and thermal shutdown. It is ideal for compact HB LED driver applications that require a wide, 100:1 dimming-control range such as interior and exterior automotive, emergency, architectural, and other lighting applications.




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